I wanted to update this thread and let you know that we are still investigating this issue, which seems to affect users of certain UK ISPs (Internet Service Providers) that are running blocking/filtering software, which is limiting their users' access to WordPress.com. Thanks for your patience while we work with those ISPs to look for a solution.

When we investigated this issue, we learned that a number of internet service providers based in the UK are now blocking sites listed by the Internet Watch Foundation. IWF flagged a site hosted on WordPress.com; we took the site down (it was in violation of our TOS), but not before some ISPs blocked it. Unfortunately, the blocking was not done very well and some of our servers were blacklisted, preventing our UK users from being able to fully access their sites. We communicated with the ISPs and IWF, and expect that things should be functioning normally soon.

We regret the inconvenience for our users, and are taking steps to make sure we don’t see a repeat of this issue in the future.